The present invention relates to emissive displays which convert electrical energy to luminous energy as a function of the image signal.
Major technologies for emissive displays include cathodoluminescence and electroluminescence. Cathodoluminescence, which is excitation arising from bombardment with a beam of electrons, is used in CRT-display systems. Electroluminescence, which is excitation resulting from the application of an ac or dc electric field, is used in electroluminescent displays, while other sources of light, such as photoluminescence, chemiluminescence and bioluminescence, exist, existing displays implementing those technologies are not acceptable, as limitations in addressability, reversibility, switching time and luminous efficiency hinder effective operation. Needs exist for display systems that eliminate or minimize the limitations encountered during the use of alternative light source technologies.
Currently, three flat-panel technologies exist: active matrix liquid crystal display systems, alternating current thin film electroluminescent systems and alternating current gas plasma systems.
Liquid crystal systems are generally lightweight, power efficient and have excellent full sunlight performance. Disadvantages realized by those systems include poor contrast, narrow viewing angles and slow reaction times. Active matrix liquid crystal displays (AMLCD) overcome some of those shortcomings by using thin-film transistors placed at each pixel. That allows for faster response times, improved contrast, wider viewing angles and superb color. Unfortunately, AMLCD has a set of associated problems, including sensitivity to environmental conditions of temperature and vibration, complex and expensive construction costs and unacceptable scalability.
Electroluminescent systems offer many advantages, including solid-state construction, inherent ruggedness and reliability, high contrast and luminance, broad viewing angles, simple pixel addressing control, high resolution and, relative to plasma display systems, are lightweight and power efficient. Electroluminescent systems, however, have poor scalability. In addition, full-color video operation support is difficult to provide using electroluminescent systems, as difficulties exist in finding blue phosphors for providing proper color saturation and luminance.
Gas plasma systems offer many advantages, including improved scalability, full color and full gray scale characteristics with wide viewing angles and solid-state construction. Those systems, however, are generally heavy and have high power consumptions, short life expectancies, limited resolution and fuzzy images.
Needs exist for display systems that offer the advantages of existing systems without realizing the limitations of those systems.